This invention relates to exhaust gas recirculation (EGR) valves for the internal combustion engines of vehicles such as automobiles, vans, and trucks, and in particular to a universal EGR valve which is easy to install, is easily connected to the vacuum tube, and is easily calibrated.
A major part of anti-pollution devices on the internal combustion engines of present day vehicles is the exhaust gas recirculation valve. EGR valves are attached to the exhaust manifold where the crossover pipe leads to the intake manifold. At that point, the valve is inserted into the exhaust manifold through a pre-existing hole to regulate the amount of exhaust entering the intake manifold. This cools the peak combustion temperature, provides a better burn of the gas and reduces NO.sub.x emissions.
There are presently two types of EGR valves, ported vacuum EGR valves and back pressure EGR valves. In the former, a tube connects the valve to the carburetor, harnessing the vacuum created by the carburetor. When the vacuum becomes strong enough, the vacuum opens the valve and allows the exhaust gas to flow freely from the crossover pipe to the intake manifold. There is no actual regulation of the flow of exhaust here.
In the latter, a back pressure transducer is interposed between the valve and the carburetor along the vacuum line. The transducer has an exhaust pressure tube which is inserted into the manifold to measure the pressure in the crossover pipe. The back pressure transducer regulates the amount of exhaust entering the intake manifold based on the pressure within the crossover pipe. When the back pressure transducer valve is opened, air is bled into the vacuum line. Thus, the EGR valve is by-passed until the pressure within the back pressure transducer reaches a specified point. When the set point is reached, the back pressure transducer valve is closed and the bypass is shut off. The vacuum then opens the EGR valve, allowing exhaust to pass to intake manifold. When the pressure drops below its set point, the bypass is again opened and the exhaust is prevented from entering the intake manifold Use of the back pressure transducer allows vehicles to reach stricter emission standards and increases fuel economy by creating an even better burn of the gas.
The problems associated with EGR valves are problems of compatibility, installation, and clogging.
Presently major car manufacturers not only use different engines but alter their engines from time-to-time. Thus on different makes and models of vehicles, the holes for the EGR valves and the EGR valves themselves vary widely. This requires a mechanic to stock hundreds of different types of valves to be able to work on a wide variety of vehicles, placing a severe financial strain on service stations and mechanics. Presently, there are no EGR valves having a base which could fit a variety of styles, makes, and models of vehicles.
Mounting problems are due partially to the fact that the valve canister often extends out over the bolt holes in the base. This provides for little maneuverability and makes securing the base to the exhaust manifold very difficult.
Mounting is also complicated by the fact that the carburetor and exhaust manifold can be in varying locations under the hood, depending on the make and model of the vehicle. Attachment is further complicated by the fact that the port on the valve, to which the vacuum tube is attached, is fixed in one direction. Thus, the vacuum tube may have to be bent 180.degree. to be attached to the valve. This problem was addressed by Hunt, U.S. Pat. No. 4,492,210. Hunt provides a back pressure EGR valve in which the valve and transducer are contained within a single canister. The canister rotates about its longitudinal axis to make connection to the vacuum hose easier The canister is mounted on a cylindrical fitting which is attached to the top of the base. The valve stem slides through the fitting and the fitting protrudes through a hole in the bottom of the canister. The canister is then held in position by means of a retaining ring. This allows the canister to rotate on the base. However, the canister has an internal spring which tends to pull the bottom of the canister away from the fitting and pulling it against the retaining ring. The force of the spring acting against the retaining ring eventually pulls the retaining ring off the fitting and the EGR valve and base must then be replaced.
The mounting problems associated with EGR valves such as Hunt's can be overcome by using a smaller canister. This can be accomplished by using an external back pressure transducer. However, there presently is no easily mounted EGR valve having remote or external back pressure transducer all connected to the same base. General Motors, in their repair kit, EGR R, supplies a remote back pressure transducer having an adapter plate which mounts to the manifold beneath the base of a ported EGR valve. This repair kit enables older model cars to meet new stringent emission standards. It may also be used as a substitute for back pressure transducers in single piece back pressure EGR valves, such as Hunt's, which have a clogged transducer. However, on GM's repair kit, the pressure tube which is attached to the adapter plate of the back pressure transducer is permanently secured and cannot rotate. This makes connection of the back pressure transducer to the EGR valve more difficult requiring more tubing between the pressure tube and the stem to make connection easier.